Method and device for producing a galvanic layer on a substrate surface

ABSTRACT

A method and a device are described for producing a galvanic layer having a defined spatial extent on an electrically conductive substrate surface having any shaped contour at all. In this context, an electrolyte jet from a nozzle is applied to the substrate, and a current flows between the nozzle and the substrate surface essentially via the electrolyte jet. The device is provided with a pump for delivering an electrolyte from an electrolyte reservoir to the nozzle and for producing an electrolyte jet directed at the substrate surface. Moreover, the device has a reactor in which are arranged the substrate to be coated, as well as the nozzle. The substrate and the nozzle are connected to a direct current source, and a configuration of the substrate and of the nozzle in the reactor is variable during the coating process.

BACKGROUND INFORMATION

[0001] The present invention is directed to a method and a device forproducing a galvanic layer having a defined spatial extent on anelectrically conductive substrate surface.

[0002] Generally, galvanically produced layers which are appliedprecisely to a limited area of a substrate surface, are described aspartial precision layers. The galvanic layers having limited spatialdimensions are produced by selectively influencing a current flow in anelectrolyte between an anode and the substrate to be coated, in agenerally known way, using screening.

[0003] It is additionally provided in the case of a so-called masktechnique, to provide the substrate surface to be coated, for example,with a photosensitive resist, which stops a current flow between theanode and the substrate in this region and prevents a deposition ofcoating material.

[0004] The known devices in which the galvanic coating processes takeplace have the disadvantage, however, of being tailored to the geometricform of the particular substrate to be coated, and also of requiringreplacement or retrofitting when another substrate or component type isto be coated. The necessity to fix the devices in position in order toproduce a galvanic layer on substrates having a specific, spatial formmakes the coating process inflexible, and a layer thickness of thepartial precision layers is only able to be influenced in its totalityby altering the process parameters of the coating process each time.

[0005] This leads disadvantageously to the situation where using devicesand methods known in the field for producing a galvanic layer on asubstrate surface, for the most part, a contour layer having a constantlayer thickness can be applied, a surface contour of the substratesurface being identically replicated by the galvanic contour layer, anda profile layer, which, in its spatial extent, has a variable layerthickness, being only able to be produced with considerable cost forequipment.

[0006] A device and a method for producing galvanic layers onelectrically conductive substrates are known from the German DE 197 36340 A1. The device is provided for producing uniformly unpatterned, aswell as patterned galvanic layers, patterned galvanic layers beingproducible using the described method.

[0007] The device of the DE 197 36 340 A1 has a bath for the electrolyteinto which the holder for the substrate and the anode connected to thevoltage source, dip. The holder is composed of a cylindrical housinghaving two open ends and one closure which can be screwed onto the onehousing end, thereby sealing it. The interior of the housing is made upof three concentrically disposed cylindrical sections. To ensureadequate movement of the electrolyte over the metal layer or thesubstrate, an agitator is provided. Alternatively, it can also beprovided, however, for the electrolyte to be suctioned out of thehousing, thereby producing the desired electrolyte motion forcompensating for concentration gradients in the electrolyte.

[0008] To produce a patterned galvanic layer on the electricallyconductive substrate surface, a mask pattern of a polymer resist isinitially applied to the one-sided metallized, dielectric substratesurface, photolithographically or using excimer laser ablation. The maskpattern is identical to the negative of the patterned galvanic layer tobe produced. A mesh for producing a patterned galvanic layer of auniform thickness is placed between the agitator and the substratesurface.

[0009] However, this device known from the related art has thedisadvantage that, prior to producing a patterned galvanic layer, it isnecessary to prepare the substrate to be coated, i.e., its surface, orthe area surrounding the substrate, i.e., the device itself, inaccordance with the layer to be produced. This preparation correspondsto the application of a photoresist or the placement of appropriatescreening to guide the current field within the electrolyte. However,such process-preparation production steps entail considerable outlay andincrease the production costs related to the coated substrates and/orcomponents.

SUMMARY OF THE INVENTION

[0010] In contrast, the method according to the present invention havingthe features of claim 1 has the advantage that galvanic layers, formedas contour or profile layers, are able to be applied to an electricallyconductive substrate surface having any shaped contour at all, withoutentailing costly process-preparation production steps.

[0011] This is achieved in that an electrolyte jet is applied to thesubstrate surface, a current flows between a nozzle and the substrateessentially via the electrolyte jet, and a configuration of the nozzleand of the substrate surface is variable during the coating process, sothat to fabricate patterned contour galvanic layers, as well aspatterned profile galvanic layers, measures are not needed to mask thecomponents or the substrate surfaces, or an arrangement of screens ormeshes is not needed, since a coating is provided essentially only inthe region of the substrate surface where the electrolyte jet impinges.

[0012] Applying the method according to the present invention whichconstitutes a “jet coating technique”, a coating of substrates, that is,to a large degree, independent of components, and a rapid adaptation tonew conditions is possible, through which means, in comparison to knowncoating techniques, such as, for example, the mask technique and/or thescreen technique, the jet coating technique exhibits a substantiallygreater flexibility.

[0013] The device according to the present invention having the featuresof claim 17 has the advantage that any desired contour of a substrate tobe coated, or its surface may be simulated, without retrofitting thedevice, and nearly every desired form of a galvanic layer may be appliedto the substrate.

[0014] For this, the device for producing a galvanic layer having adefined spatial extent on an electrically conductive substrate surfacehaving any shaped contour at all, is provided with a pump for deliveringan electrolyte from an electrolyte reservoir to a nozzle and forproducing an electrolyte jet directed at the substrate surface, and witha reactor in which are arranged the substrate to be coated, as well asthe nozzle, and with a direct current source which is connected to thesubstrate and the nozzle. Moreover, an arrangement of the nozzle and/orof the substrate during the coating process in the reactor is variable,so that the electrolyte jet or the nozzle is able to be guided similarlyto a pin with respect to the substrate surface. Thus, the galvanic layeris able to be applied with a specific contour or with a specific profileto the desired regions of the substrate surface.

[0015] Moreover, it is advantageous that substrates having any desiredsurface contour, such as rotationally symmetric bodies, substrateshaving grooves or depressions, but also flat plates, are able to beprovided with a galvanic layer in a simple manner. In this context, itis particularly advantageous that a change in the substrate type doesnot necessitate retrofitting the device according to the presentinvention, since any surface contour at all is able to be covered by thenozzle. In the present connection, the term “substrate type” is to beunderstood as a variable geometric form of the substrate to be coated.

[0016] Further advantages and refinements of the present invention arederived from the description, the drawing, and the claims.

BRIEF DESCRIPTION OF THE DRAWING

[0017] An exemplary embodiment of the device according to the presentinvention for producing a galvanic layer on a substrate surface is shownin a schematically simplified version in the drawing and is elucidatedin more detail in the following description. in which:

[0018]FIG. 1 shows a method flow chart of a device or system forproducing a galvanic layer on a substrate surface;

[0019]FIG. 2 a nozzle and a substrate, an electrolyte jet whichconstitutes a free jet being applied to the substrate;

[0020]FIG. 3 the nozzle and the substrate according to FIG. 2, theelectrolyte jet being an immersion jet;

[0021]FIG. 4 a schematic representation of a substrate, on which alocally limited galvanic layer is applied, a superposition ofgalvanically produced individual spots being represented in the rightillustration; and

[0022]FIG. 5 a comparison of a profile layer applied to a substrate anda contour layer applied to a substrate.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0023]FIG. 1 shows a device 1 for producing a galvanic layer having adefined spatial extent on an electrically conductive substrate surface 2which has a pump 3 for delivering an electrolyte 4 from an electrolytereservoir 5 to a nozzle 6 and for producing an electrolyte jet 7directed to substrate surface 2. In addition, device 1 has a reactor 8in which are placed substrate 9 to be coated as well as nozzle 6,substrate 9 and nozzle 6 each being connected to a direct current source10.

[0024] Reactor 8 has a protective container 11 and a substrate holder 12or workpiece holder configured in the protective container. In addition,between nozzle 6 and pump 3, a valve 13 is provided for controlling adelivery quantity of electrolyte 4. In parallel to a connection line 14between pump 3 and valve 13 is a line 15 which, starting fromelectrolyte reservoir 5, leads into connection line 14 upstream fromvalve 13 and is provided with a further valve 16. Thus, the deliveryquantity of electrolyte 4 to nozzle 6 is adjustable by way of valve 13and additional valve 16, as well as by way of the conveying capacity ofpump 3.

[0025] Protective container 11 is connected via a further connectionline 17 to electrolyte reservoir 5, further connection line 17 beingblockable via a shutoff valve 18 and being provided for recirculatingelectrolyte 4 into electrolyte reservoir 5.

[0026] To ensure a proper functioning of device 1, electrolyte reservoir5 is equipped with a device 19 for tempering electrolyte 4, so that thecoating process is substantially independent of the ambienttemperatures. Situated underneath reactor 1 and electrolyte reservoir 5is a catch pan 20 used to collect electrolyte flows escaping from theclosed system in the case of possible leakage from reactor 8,electrolyte reservoir 5, and the line system of device 1, and to avoidcontaminating the environment with electrolytes potentially containingsubstances harmful to health and the environment.

[0027] Device 1 is designed to be able to operated in a so-calledfree-jet operation or in a so-called immersion jet operation.

[0028] During the free-jet operation of device 1 in accordance with therepresentation in FIG. 2, nozzle 6 situated in protective container 11and substrate 9 are not immersed in electrolyte 4. Electrolyte jet 7emanating from nozzle 6 is applied in empty protective container 11 as afree jet to substrate 9. In this context, the diameter of electrolytejet 7 corresponds to the nozzle diameter and only increases slightly insize with increasing distance from nozzle 6. In the area of an impactpoint 21 on substrate surface 2, electrolyte 4 on substrate surface 2flows away “to the outside”, i.e., radially outwardly from electrolytejet 7, and collects in the bottom area of protective container 11. Fromthere, electrolyte 4 flows via further connection line 17 back intoelectrolyte reservoir 5, shutoff valve 18 being opened.

[0029] During immersion jet operation of device 1, shutoff valve 18 isclosed, so that electrolyte 4 is accumulated in protective container 11,and is fed back via an output 22 to electrolyte reservoir 5. This meansthat in the immersion jet operation of device 1, substrate 9, as well asnozzle 6 are immersed in electrolyte 4, i.e., protective container 11 iscompletely filled with electrolyte 4, and electrolyte jet 7 is formed asflow threads in electrolyte 4. In this context, electrolyte jet 7 widenswith increasing distance from nozzle 6, i.e., its diameter increasinglyenlarges. From an impact region 21 on substrate surface 2, electrolytejet 7 flows off radially, directed toward substrate surface 2.

[0030] The course of electrolyte jet 7 during free-jet operation, aswell as during immersion-jet operation of device 1, is shown greatlyschematized in FIGS. 2 and 3, respectively. It proceeds from these basicrepresentations that the impact region of electrolyte jet 7 in thefree-jet operation of device 1 has a smaller diameter than in theimmersion-jet operation.

[0031] In the context of the method according to the present inventionfor producing a galvanic layer having a defined spatial extent on asubstrate surface having any shaped contour at all, nozzle 6 isessentially directed at an electrically conductive, i.e., metallicsurface of substrate 9. Electrolyte 4 flows as a liquid jet throughnozzle 6 and meets with substrate surface 2 to be coated, i.e., aworkpiece surface. In this context, nozzle 6 is designed as anelectrode, so that electric current is able to flow via electrolyte 4,i.e., electrolyte jet 7, to substrate 9, and a metal deposition iseffected on a narrowly restricted area around impact region 21, i.e.,the impact point of electrolyte jet 7.

[0032] The coating point is primarily described as spot 25, the diameterof this spot 25 being determined by the flow shape, the nozzle diameterof the electrolyte jet, the flow velocity of electrolyte jet 7, as wellas by the distance between nozzle 6 and substrate 9. Here, the flowshape of electrolyte 4 is to be understood as whether electrolyte 4 isapplied to substrate surface 2 in the form of an immersion jet or a freejet.

[0033] A change in or enlargement of the vertical distance of nozzle 6from substrate surface 2 effects that the layer profile becomesincreasingly flatter, and the diameter of spot 25 increases, this trendbeing more pronounced in free-jet operation than in immersion-jetoperation.

[0034] A height of spot 25 or of the coating is adjusted as a functionof a time during which the current flows between nozzle 6 and substratesurface 2. A further parameter of the coating process which influencesthe height of spot 25 is the magnitude of the applied current intensity,a greater amperage effecting an intensified deposition, the height ofspot 25 being greater, and the diameter of spot 25 remaining essentiallythe same.

[0035] In a schematized representation, FIG. 4 shows substrate 9 whichis coated with a spot 25. To produce a flat expansion of a galvaniclayer on substrate surface 2, a plurality of individual spots 25 arearranged in a series. To produce a profile layer, a plurality of spots25 are superposed, this being referred to as superposition.

[0036] To implement a superposition, it is provided to move theworkpiece to be coated or substrate 9 and/or nozzle 6 during the coatingprocess, so that a contour layer or a profile layer may be produced in asimple manner on substrate 9. In this manner, the need is eliminated fora conventional mask and screen technique to selectively coat a substratesurface. Moreover, preparatory production steps, such as applying aresist layer to substrate surface 2, or retrofitting a coating deviceare eliminated.

[0037] By moving substrate 9 or nozzle 6, a vertical distance betweenthem may be altered, for example to form a profile layer 23, as depictedin FIG. 5, on substrate surface 2. Furthermore, the nozzle and/orsubstrate 9 may be moved to change impact region 21 of the electrolytejet on substrate surface 2, so that a contour layer having a uniformlayer thickness may be produced on the substrate surface.

[0038] Of course, deviating herefrom, it is within the discretion of oneskilled in the art to execute the individual movements of nozzle 6 andof substrate 9 in combination. This means that the vertical distancebetween nozzle 6 and substrate surface 2, and also impact region 21 ofelectrolyte jet 7 on substrate surface 2 are suitably changed. Thus, agalvanic layer may be precisely applied to substrate surface 2 and witha defined spatial extent, and with any shaped contour at all. A contourlayer 24 of this kind is shown in the right representation of FIG. 5,contour layer 24 having a constant layer thickness, and the surfacecontour of substrate 9 being identically replicated by contour layer 24.

[0039] To move nozzle 6 and substrate 9, a positioning unit is providedfor nozzle 6, and for substrate 9 or substrate holder 12. Thepositioning unit is not shown here in greater detail in the drawing andmay be designed as a robot, similarly to resist technology. By designingdevice 1 in this manner, it is possible for the nozzle to be driven intogrooves or other depressions in substrate surface 2 and, there, for agalvanic layer having the desired contour or desired profile to beproduced. One possible application case is, for instance, coatingcomponents of a valve. It is conceivable in this context, on a seat areaof a valve tappet, to place a ring at the crown rim, so that this ringrests only at the rim and not in the entire area of the crown at thevalve seat.

[0040] Using the present jet-coating technique, which provides fordepositing a metal layer in the form of a spot 25 as the result ofimpact of electrolyte jet 7 on substrate surface 2, it is possible toproduce galvanic layers having any desired pattern delineation at all asa contour or profile layer on a substrate surface, since the coating inimpact region 21 in the form of spot 25, even in the free-jet operationof device 1, does not come in contact with air or oxygen. In thismanner, a passive surface layer is prevented from forming on the alreadyapplied metal layer, because a liquid film or an electrolyte film flowspermanently over spot 25. For this reason, it is possible to build upfurther spots on a deposited spot 25 or to place them next to it, theindividually applied spots, among themselves, forming a permanent bond.

[0041] Various series of measurements have revealed that, in thefree-jet operation of device 1, high elevated spots 25 formed with asmall diameter are produced on substrate surface 2. In the immersion-jetoperation of device 1, flatter spots 21 having a larger diameter areproduced on substrate surface 2, since the greater flow resistance ofelectrolyte 4 surrounding electrolyte jet 7, causes it to widen withincreasing distance from nozzle 6.

What is claimed is:
 1. A method for producing a galvanic layer having adefined spatial extent on an electrically conductive substrate surface(2) having any shaped contour at all, an electrolyte jet (7) beingapplied by a nozzle (6) to the substrate surface (2), and a currentflowing between the nozzle (6) and the substrate surface (2) essentiallyvia the electrolyte jet (7), a configuration of the nozzle and of thesubstrate surface being variable during the coating process.
 2. Themethod as recited in claim 1, wherein the electrolyte jet (7) is a freejet.
 3. The method as recited in claim 1, wherein the electrolyte jet(7) is an immersion jet.
 4. The method as recited in one of claims 1through 3, wherein parameters of the coating process are provided insuch a way that the substrate surface (2) is essentially coated in theimpact region of the electrolyte jet (7) on the substrate surface (2).5. The method as recited in claim 4, wherein a diameter of the coatedregion (25) is adjusted as a function of the diameter of the nozzle (6),and/or as a function of the flow velocity of the electrolyte (4), and/oras a function of a vertical distance between the nozzle (6) and thesubstrate surface (2).
 6. The method as recited in one of claims 1through 5, wherein a height of the coating (25) is adjusted as afunction of a time during which the current flows between the nozzle (6)and the substrate surface (2), and/or as a function of the currentintensity.
 7. The method as recited in one of claims 1 through 6,wherein the nozzle (6) and/or the substrate (9) are moved during thecoating process.
 8. The method as recited in claim 7, wherein the nozzle(6) and/or the substrate (9) are moved to vary the vertical distancebetween them, the vertical distance being varied, in particular, in sucha way that a profile layer (23) is produced on the substrate surface(2).
 9. The method as recited in claim 7, wherein the nozzle (6) and/orthe substrate (9) are moved to vary the impact region (21) of theelectrolyte jet (7) on the substrate surface (2), the impact region (21)being varied, in particular, in such a way that a contour layer (24) isproduced on the substrate surface (2).
 10. The method as recited inclaim 7, wherein the nozzle (6) and/or the substrate (9) are moved tovary the vertical distance between them and to vary the impact region(21) of the electrolyte jet (7) on the substrate surface (2).
 11. Themethod as recited in one of claims 1 through 10, wherein a plurality ofelectrolyte jets is applied simultaneously to the substrate surface. 12.A device for producing a galvanic layer having a defined spatial extenton an electrically conductive substrate surface (2) having any shapedcontour at all, comprising a pump (3) for delivering an electrolyte (4)from an electrolyte reservoir (5) to a nozzle (6) and for producing anelectrolyte jet (7) directed to substrate surface (2), a reactor (8) inwhich are placed the substrate (9) to be coated as well as the nozzle(6), and a direct current source (10) which is connected to thesubstrate (9) and the nozzle (6), a configuration of the nozzle (6)and/or of the substrate (9) in the reactor (8) being variable.
 13. Thedevice as recited in claim 12, wherein the reactor (8) has a protectivecontainer (11) and a substrate holder (12) configured in the protectivecontainer (11).
 14. The device as recited in claim 12 or 13, wherein avalve (13) for controlling a delivery quantity of the electrolyte (4) isprovided between the nozzle (6) and the pump (3).
 15. The device asrecited in claim 13 or 14, wherein the protective container (11) isconnected to the electrolyte reservoir (5), and this connection isblockable via a shutoff valve (18).
 16. The device as recited in claim15, wherein in a free-jet operation, the shutoff valve (18) is opened,and, in an immersion-jet operation, the shutoff valve (18) is closed,during the immersion jet operation, the electrolyte (4) is accumulatedin the protective container (11), and is fed back via an output (22) tothe electrolyte reservoir (5).
 17. The device as recited in one ofclaims 12 through 16, wherein the electrolyte reservoir (5) is equippedwith a device (19) for tempering the electrolyte (4).
 18. The device asrecited in one of claims 13 through 17, wherein the nozzle (6) and/orthe substrate holder (12) are provided with a controlled positioningdevice for guiding the nozzle (6) and/or the substrate holder (12)during the coating process.